Method and apparatus of cooking food in a lightwave oven

ABSTRACT

A lightwave oven cooking method and apparatus using power and pulsed power applied to a plurality of high-power lamps which provide radiant energy in the electromagnetic spectrum and having wavelengths including the visible and near-visible ranges wherein irradiation is applied to the food by applying power to the lamps for a specified period of time without vaporizing all of the surface water on the food, and then applying reduced irradiation to the food to complete the cooking cycle without producing an overly browned surface which inhibits deep penetration of radiation in the near-visible and visible ranges. The reduced power can be at a reduced duty cycle which can be done in a sequence of one or more reducing steps in the duty cycle or a continuous reduction of the duty cycle of the power applied to the lamps. A change in water vapor concentration emitted from the surface can be sensed to reduce power.

CROSS REFERENCES TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.08/146,415, filed Nov. 1, 1993, allowed, which application is acontinuation-in-part of U.S. patent application Ser. No. 738,207 filedon Jul. 30, 1995, (now abandoned) which was a continuation-in-part ofU.S. patent application Ser. No. 350,024 filed on May 12, 1989, now U.S.Pat. No. 5,036,179 issued Jul. 30, 1991; and a continuation-in-part ofU.S. patent application Ser. No. 769,370, filed Oct. 1, 1991, (nowabandoned), which was a continuation of U.S. patent application Ser. No.664,494, filed Mar. 5, 1991 (now abandoned), which was a continuation ofU.S. patent application Ser. No. 195,967, filed May 19, 1988 (nowabandoned).

FIELD OF THE INVENTION

This invention relates to the field of cooking method and apparatus.More particularly, this invention relates to the use of power and pulsedpower applied to high-power lamps providing radiant energy in theelectromagnetic spectrum including a significant portion in thenear-visible and visible ranges.

BACKGROUND OF THE INVENTION

Ovens for cooking and baking food have been known and used for thousandsof years. Basically, oven types can be categorized in four cookingforms; conduction cooking, convection cooking, infra-red radiationcooking and microwave radiation cooking.

There are subtle differences between cooking and baking. Cooking justrequires the heating of the food. Baking of a product from a dough, suchas bread, cake, crust, or pastry, requires not only heating of theproduct throughout but also a chemical reaction coupled with driving thewater from the dough in a predetermined fashion to achieve the correctconsistency of the final product and finally browning the outside.Following a recipe when baking is very important. An attempt to decreasethe baking time in a conventional oven by increasing the temperatureresults in a damaged or destroyed product.

In general, there are problems when one wants to cook or bake foodstuffswith high-quality results in the shortest times. Conduction andconvection provide the necessary quality, but both are inherently slowenergy transfer methods. Long-wave infra-red radiation can providefaster heating rates, but it only heats the surface area of mostfoodstuffs, leaving the internal heat energy to be transferred by muchslower conduction. Microwave radiation heats the foodstuff very quicklyin depth, but during baking the loss of water near the surface stops theheating process before any satisfactory browning occurs. Consequently,microwave ovens cannot produce quality baked foodstuffs, such as bread.

Radiant cooking methods can be classified by the manner in which theradiation interacts with the foodstuff molecules. For example, startingwith the longest wavelengths for cooking, the microwave region, most ofthe heating occurs because of the coupling of radiant energy into thebipolar water molecule causing it to rotate and thereby absorb energy toproduce heat. Decreasing the wavelength to the long-wave infra-redregime, we find that the molecules and their component atoms resonantlyabsorb the energy in well-defined excitation bands. This is mainly avibrational energy absorption process. In the near-visible and visibleregions of the spectrum, the principal absorption mechanism isexcitation of the electrons that couple the atoms to form the molecules.These interactions are easily discerned in the visible band of thespectra, where we identify them as "color" absorptions. Finally, in theultraviolet, the wavelength is short enough, and the energy of theradiation is sufficient to actually remove the electrons from theircomponent atoms, thereby creating ionized states. This short wavelengthultraviolet, while it finds uses in sterilization techniques, probablyhas little use in foodstuff heating, because it promotes chemicalreactions and destroys food molecules.

SUMMARY OF THE INVENTION

Broadly stated, the present invention is directed to method andapparatus for cooking food in a lightwave oven having a plurality ofhigh-power lamps providing radiant energy in the electromagneticspectrum including a significant portion in the near-visible and visibleranges wherein irradiation is applied to the food by applying power tothe lamps for a period of time and without vaporizing all of the surfacewater on the food and then applying reduced irradiation to the food. Inaccordance with this invention, thick foods can be cooked with deeppenetrating visible and near-visible light radiation without producingan overly browned surface which will absorb the radiation at the surfaceand will reduce the amount of visible and near-visible light radiationwhich can penetrate deeply into the food.

In accordance with the preferred embodiment of the present invention,the reduced irradiation is produced by applying power to the lamps at areduced duty cycle which can either be done in a sequence of one or morereducing steps in the duty cycle or a continuous reduction of the dutycycle of the power applied to the lamps.

A feature and advantage of this invention is that water from deep withinthe food can migrate to the surface and prevent the surface from beingheavily browned by infra-red radiation that would then inhibit deeppenetration of radiation in the near-visible and visible ranges.

In accordance with another aspect of the present invention, full poweris first applied to the lamps for irradiating the food withoutvaporizing all of the surface water from the food and thereafter poweris applied to the lamps at a reduced duty cycle as the flow of water tothe surface of the food decreases.

In accordance with another aspect of the preferred embodiment of thepresent invention, the lamps are turned off or radiation to the foodeliminated periodically, preferably in between application of power tothe lamps at different duty cycles whereby water is replenished fromwithin the food onto the surface of the food.

In accordance with still another aspect of the present invention, achange in the color or the surface of the food of a given degree issensed and irradiation of the food then terminated to allow water fromwithin the food to reach the surface of the food.

In accordance with still another aspect of the present invention and asa final step for cooking the food, the duty cycle of the power to thelamps is increased from an operating duty cycle level for browning thefood when the desired level of cooking has been accomplished deep withinthe food or the duty cycle can be established that allows a slowbrowning reaction throughout the latter portion of the cycle so thatfinal heating and browning occur simultaneously.

By providing a sufficiently intense source of visible and near-visibleradiation in conjunction with the longer infra-red radiation over anextended period of time while the duty cycle of the power to the lampsis reduced, a novel and very effective cooking method and apparatusresults, especially for cooking thicker foods.

The low absorption of visible and near-visible radiation allows theenergy to penetrate the foodstuff and heat it deeply like microwaveenergy. By contrast the longer infra-red radiation does not penetratevery deeply and acts as a very effective browning agent. By combiningthese sources of radiation into a single cooking process it is possibleto produce a very rapid and highly efficient method of cooking andbaking a wide variety of foodstuffs.

Using intense visible, near-visible, and infra-red radiation to cookfood has a number of significant advantages. First of all, the cookingprocess is very fast. Bakery products, like pizza crust for example, canbe baked five to ten times faster than ovens that rely on conventionalconvection and conduction processes only. Large, thick meat and poultryproducts, such as roasts and whole chickens and turkeys, can be cookedthree to five times faster than by convection and conduction processesalone. Second, the quality of the cooking process is enhanced for manyfoodstuffs. For example, crusts become fully cooked with crispyexteriors and moist, chewy interiors. Vegetables are cooked so fast thatthey are virtually steamed in their own water vapor, leaving them hot,but with very little loss of any of their nutritive values. Third, theprocess is very energy efficient. Because the oven has reflective innerwalls, a large fraction of the energy produced by the sources is used tocook the food rather than heat the oven. A pizza can be fully baked forabout $0.01 of electrical energy.

Additionally, the present invention enables the fast cooking timesavailable with microwave energy but with a more flavorful taste and amore traditional texture and surface coloring as in convection andinfra-red cooking.

These and other aspects, features and advantages of the presentinvention will become more apparent upon a perusal of the followingspecification taken in conjunction with the accompanying drawingswherein similar characters of reference refer to similar items in eachof the several views.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a front cross section of a preferred embodiment of thepresent invention.

FIGS. 1A and 1B are fragmentary views of a portion of FIG. 1illustrating alternative embodiments of the present invention.

FIG. 2 shows a side cross section of the preferred embodiment of thepresent invention.

FIG. 3 is a graph showing the approximately inverse linear relationshipbetween cooking power and cooking time.

FIG. 4 is a graph showing the constant power-time product for baking apizza in the oven of the preferred embodiment.

FIG. 5 is a graph showing a power-time illustration for applying powerat different duty cycles to lamps for radiating a food product with thisinvention.

FIGS. 6, 7 and 8 are graphs similar to FIG. 5 showing alternativeembodiments of this invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIGS. 1 and 2 are front and side cross sectional views of the apparatusof a preferred embodiment of the present invention. The oven in FIG. 1includes an outer enclosure 10. The enclosure has an inner wall 12coupled to the outer wall 10. Ordinarily, an insulating layer 14 isformed between the outer enclosure 10 and the inner wall 12. Because ofthe inherent speed of the cooking cycle, the insulating layer 14 may bea layer of air.

The present invention has been used to cook pizzas reasonablycontinuously for an hour in an oven with only air as an insulator. Whilethe exterior of the oven did warm up, it never became too warm to touchcomfortably. This is true because the interior walls of the oven arereflective so that a large fraction of the energy is used to cook thefood, not heat the oven. Second, a fan is used to pull hot air out ofthe oven. Though some air is heated directly by the radiation, most ofthe air is heated by convection from the cooked food. Because thecooking times are so short with the present invention, the hot air isremoved to prevent further cooking after the radiation source is turnedoff.

The energy for cooking is supplied by the lower radiation heating lamps16 and the upper radiation heating lamps 18. These lamps are generallyany of the quartz body, tungsten-halogen or quartz arc lampscommercially available, e.g., 1.5 KW 208 V quartz-halogen lamps. Theoven according to the preferred embodiment utilizes ten such lamps andcooks with approximately forty percent (40%) to fifty percent (50%) ofthe energy in the visible and near-visible light portion of thespectrum, which is significant. Quartz xenon-krypton arc lamps have beenused as an alternate source in which ninety-five percent (95%) of theradiation is below 1 μm and good cooking results have been achieved withtheir shorter wavelengths.

There is no precise definition for the range of wavelengths for visiblelight because the perceptive ranges of each human eye is different.Scientific definitions typically encompass the range of 0.39 μm to 0.77μm. An engineering shorthand for visible light specifies the range of0.4 μm to 0.7 μm. The term "near-visible" has been coined for radiationthat has wavelengths longer than the visible range, but less than thewater absorption cut-off at 1.35 μm. The term "long-wave infra-red"refers to wavelengths greater than 1.35 μm.

The inner surface of the inner wall 12 is preferably a highly polished,poorly absorptive surface, so that it appears to be very reflective tothe wide spectrum of wavelengths from the radiant lamps. Polishedaluminum and stainless steel have been successfully used for the innerwall 12. Plating the inner wall 12, such as with gold, increased theefficiency of the reflector for visible light by about ten percent (10%)over the polished aluminum walls. Two radiation transparent plates 20and 24 are used to isolate the cooking chamber from the radiant sourcesmaking the oven easier to clean as shown in FIG. 3. These plates can beformed from such materials as quartz, glass or pyroceramic that transmitvisible, non-visible and infra-red radiations. The lower transparentplate 20 is supported by brackets 22a and 22b and is positioned abovethe lower lamps 16. The upper transparent plate 24 is supported bybrackets 26a and 26b and is positioned below upper lamps 18.

Brackets 28a and 28b support a platter 30 which is positioned above thelower transparent plate 20 and below the upper glass plate 24. A fooditem 32 is positioned on platter 30 to be cooked.

The platter 30 may formed of a material similar to the transparentplates 20 and 24 to allow even cooking over the surface of the food item32. However, in some circumstances it may be desirable to crisp thebottom of the food item 32. As a particular example, when cooking apizza, it is desirable that the crust be light and crispy, rather soggyand doughy. In such an application, the cooking platter 30 can be formedof a radiation absorbing, heat conducting material, such as blackanodized aluminum. In this way, the lower lights 16 would rapidly heatthe platter 30 to a high temperature in order to crisp and brown thebottom of the pizza. It may also be desirable to perforate the platter30 in order to allow steam to escape from the cooking pizza dough.Alternatively, the platter could also be a grill structure. Platter 30should touch the support brackets 28a and 28b over very limited areas,so that the heat delivered to platter 30 is not lost by conduction.

The lamps 16 and 18 produce very high intensity visible and infra-redradiation. Prior art uses of radiant energy heat sources teach cookingusing radiation in the infra-red portion of the electromagneticspectrum. For example, see Malick U.S. Pat. No. 4,481,405 and BassettU.S. Pat. No. 4,486,639. Burkhart, in U.S. Pat. No. 4,516,486, disclosesa radiant energy cooker for the exclusive purpose of charting thesurface of foods, particularly meats.

The use of high intensity visible radiation provides a very rapid methodof high quality cooking and baking both alone or in combination withinfra-red radiation. The radiant energy from the lamps 16 and 18radiates from each bulb in all directions. A portion of the energyradiates directly onto the food item 32. The remainder of the energywill be reflected off the surface of the preferably metal inner wall 12and then strike the food item 32 for more efficient cooking.

A power supply 34 provides the power for the lamps 16 and 18, theoperation of which is controlled by a control circuit 36, shown as acircuit block.

It is possible to control the power level and/or duty cycle of each ofthe lights 16 and 18 independently with the control circuit 36. Thecontrol circuit 36, shown as a circuit block in FIG. 3, may include amicroprocessor or a microcontroller and associated memory to storeindividual cooking recipes to control proper heating of the foodproduct.

For example, in cooking a pizza, it may be desirable to run the upperlamps 18 at a reduced power level for a time. For a pizza having freshvegetables, this would prevent the overcooking of the vegetables makingthem mushy. The lower lamps 16 might be operated at a higher power levelto make the pizza crust light and crispy.

In the preferred embodiment as shown in FIG. 2, there are five lowerlamps 16a through 16e and five upper lamps 18a though 18e. Byappropriately selecting the lateral spacing between the lamps relativeto the food, even cooking can be achieved over the entire surface. Adoor 40 is also shown.

Experimental results show that cooking with one 1.5 KW lamp above andone below, i.e. impinging a maximum of 3 KW of radiant energy onto apizza, does not achieve the dramatic improvement in speed that ispossible according to the present invention. The oven in the preferredembodiment includes five lamps above and five lamps below. This numberprovides for a maximum of 15 KW of cooking energy.

Pizza has been successfully cooked using a modification of the presentinvention with more powerful bulbs using total power in the range inexcess of 4 KW to approximately 24 KW. There appears to be no reasonpreventing the power ranges in excess of 20 KW. This is a significantadvantage of the present invention. Cooking times can be reduced byincreasing power. The only way to increase power in a conventional ovenis to increase temperature which damages the food.

While cooking a pizza using total power in excess of about 4 KW anapproximately inverse linear relationship develops between time andcooking power. In other words, as the power delivered to the pizza isdoubled, the time to cook a pizza is cut in half. This result is totallyunexpected in view of conventional oven baking where increasing oventemperature to achieve a higher energy transfer rate results in a burntproduct which may have an uncooked interior.

FIG. 3 is a graph showing the power-time product versus power for bakinga pizza in the oven of the preferred embodiment. Note that in thepreferred oven the power-time product is constant and has a value ofabout 470 KW-sec.

This cooking in the linear range of the power-time product appears to bea function of both the wavelength of radiation and the amount of powerapplied. Thus, the specific mechanical configuration of the oven in thepreferred embodiment is not critical to the invention. Rather, it is thecombination of the lamps that provides at least a significant portion ofradiation in the visible and near-visible light range with total radiantpower in excess of 4 KW and impinging the radiation directly onto thefood item of energy which provides the dramatic speed increase of thepresent invention.

For example, an oven having a reflective inner surface could operateaccording to the present invention with a single arc lamp capable ofproducing sufficient power in the desired frequency ranges. In certaincircumstances it may be desirable in such a single source oven to placethe food product, such as a pizza, on a highly thermally conductiveplatter with the lamp positioned above the food item. The amount ofheating to the bottom of the pizza can be regulated by heating theplatter and by adjusting the ratio of the size of the pizza to the sizeof the pan. In other words, the amount of exposed area of the pan wouldcontrol the amount of energy absorbed by the pan used to heat the bottomof the pizza.

Microwave ovens cannot be used in cooking high quality freshly preparedpizza. The commercially available frozen pizzas for microwave ovens areprecooked and then frozen. The pizza is merely heated to the properserving temperature in the microwave oven, but the result is usuallyunsatisfactory. A higher quality pizza can be baked in a commercialgrade conduction/convection oven. There, the pizza is placed directly onthe hot floor of the oven to properly crisp the bottom of the crust (upto 900° F. in a brick oven). Unfortunately, the ovens have various "hot"spots and require constant operator attention to avoid over or undercooking the pizza, i.e., consistency is a major problem. Such ovens cooka pizza in 5 to 20 minutes. Conveyorized infra-red and hot airconvection ovens can cook a pizza in 5 to 15 minutes, but have greatdifficulty in properly crisping the bottom of the pizza.

A pizza can be cooked using the present invention in as little as 30 to45 seconds. This speed is very important in the commercial pizza marketbecause it enables pizza to be produced in a manner that would qualifyit as a true fast-food.

The energy efficiency of the present invention is illustrated by thefact that the energy cost to cook such a pizza is about $0.01. Themajority of the radiant energy produced by the oven is utilized incooking the pizza and after the cooking process is completed the energyis turned off. In contrast, conventional commercial pizza ovens must bepreheated to desired cooking temperatures. Ordinarily, the oven in apizza restaurant is left on all day, whether cooking a pizza or not,making the energy consumption significant.

In accordance with the present invention, not only thick pizza, but mostimportantly, thicker and more dense foods such as steaks, roasts,chicken, turkey, etc. are advantageously cooked by time varied pulsingthe amount of radiation directed onto the food substance.

With reference to FIG. 5, the power directed to the lamps being used tocook the food in the preferred embodiment is initiated at a maximum orgiven level 40 for a period of time T₁. At this intensity radiation inthe near-visible and visible light range penetrates deeply into thefood. The radiation in the infra-red range which does not penetratedeeply into the food is principally responsible for browning the surfaceof the food which happens typically when you get to 300°-400° F. Steamgoes off the surface at 212° F. so as long as surface water or moistureis present browning will not occur. Browning of the surface inhibitstransmission of the visible light therethrough. Therefore, for deepcooking with a lightwave oven in accordance with the present inventionit is desired to keep water on the surface the temperature of thesurface at or below 212° F. as long as possible.

In the initial cooking stage during time period T₁ the combination ofradiation in the infrared, near-visible and visible ranges does notvaporize all of the surface water on the food which includes watermigrating to the surface of the food due to the cooking process both atthe surface and deep within the food. Thus, the length of time period T₁is established by experimentation or otherwise such as by sensing thetemperature of the surface and/or the presence of steam and/or a colorchange in the surface indicative of initiation of the browning processwith a sensor 38 to terminate period of time T₁ before all the surfacewater is removed from the food. Thus, the cooking process is designed sothat browning on the outside is well controlled in such a way thatbrowning of the outside surface does not occur before the inside of thefood has been cooked. After time T₁, radiation directed to the food iseliminated for a period of time T₂ during which water is replenishedfrom within the food onto the surface of the food. The elimination ofradiation is preferably accomplished by turning off the power to thelamps but can also be accomplished by shielding the food from radiationfrom the lamps.

After the time period T₂ reduced radiation is applied to the foodtypically by reducing the duty cycle of the power to the lamps (e.g., tofifty percent (50%) duty cycle) for a period of time designated T₃ inFIG. 5. In the preferred embodiment of the invention the power pulsesduring the reduced duty cycle T₃ are maintained at the same maximum orpreset power level 40 for applying the near-visible and visible light tothe maximum depth within the food. Since during energization of thetypical high-power lamps the percentage of infra-red radiation is thehighest, periodically shielding the food from the radiation of the lampsmay be preferable under certain circumstances to actually turning offthe power to the lamps.

After irradiating the food at a reduced duty cycle during time periodT₃, radiation can be eliminated from the food for a another period oftime T₄ followed by the application of additional radiation at a secondand still lower duty cycle (e.g., for a ten percent (10%) duty cycle)for a time period T₅. The time periods T₁ -T₅ are selected so that themaximum amount of near-visible and visible radiation can pass deeplyinto the food without being obstructed by the effect of browning of thesurface resulting from infra-red radiation applied to a surface with nosurface water. The individual time periods can be determined byexperimentation in the manner described below, or the time periods canbe arbitrarily set based on experimentation with other foods and thenused on the given food and kept or adjusted depending on the results.

Depending upon the particular food, the power level and the duty cycle,the elimination of radiation in time periods T₂ and T₄ can be dispensedwith so that the time periods T₁, T₃ and T₅ can occur sequentiallywithout intervening time periods T₂ and T₄.

Sensor 38 can be used to monitor the surface of the food and to signal achange in the color of the surface of the food of a given degree so asto then trigger termination of one of the time periods T₁, T₃ or T₅,thereby allowing replenishment of surface water from within the food.

As shown in FIG. 1A, an optical sensor 38A is aimed at the surface ofthe food and senses the water vapor concentration emitted from thesurface of the food so that the control circuit 36 can terminateirradiation of the food when that concentration reaches a predetermineddegree.

FIG. 1B illustrates a sensor 38B aimed across the oven cavity forsensing water vapor emitted from the surface of the food. The controlcircuit 36 determines the decrease or absence of steam for terminatingirradiation of the food.

For providing a desired aesthetic brown surface and/or harder surfacetexture, a final period can be provided with increased radiation to thefood surface for time T₆. During time period T₆, the lamps may berestored to full power as indicated in FIG. 5 or the duty cycle fromtime period T₅ can be increased to the duty cycle of time period T₃ orsome other duty cycle 6.

By way of example, experimentation for cooking with the presentinvention to establish a preferred cooking recipe for a given food canproceed as follows. You take an example of the food made up of thespecified ingredients, such as for a muffin, and you place that food inthe oven and turn on the lamps at full power for a first very long timeperiod T₁ which is much longer than it typically will take and watch thecooking process to observe when the surface begins to brown. In the caseof a muffin cooked with a lightwave oven of this invention, usually by30 seconds you see that the surface is starting to brown. You thenprovide a safety factor by subtracting a number of seconds, for examplefive seconds, from the time at which browning was first noticed toestablish the first time period T₁ for the muffin cooking recipe. Youthen put another muffin in the oven and follow the cooking cycle with T₁equal to 25 seconds and then a prolonged reduced duty cycle (i.e., fiftypercent (50%)) for a prolonged time period T₃. When you observe themuffin starting to brown during time period T₃, you stop the cookingcycle and subtract a number of seconds, for example five, from theshortened time period T₃ and then proceed with a third muffin todetermine the time period T₅ until a muffin properly cooked and properlybrowned is achieved. Then this final cooking recipe of selected timesT₁, T₃ and T₅ is utilized and can be adjusted if needed. As set forthabove, the termination of each of the time periods T₁, T₃ and T₅ in theforegoing experiment can be selected using an optical sensor to sense agiven change in the color of the surface of the food or other parameterssuch as the temperature of the muffin surface and/or the decrease or anabsence of steam in the oven.

As an alternative to the step-wise reduction of the duty cycle from fullduty cycle during T₁ to a first reduced level of duty cycle during T₃and to a second further reduced duty cycle during T₅, the duty cycle canbe continuously reduced over a given period of time as shown in FIG. 6wherein the duty cycle is shown as decreased from one hundred percent(100%) to seventy percent (70%) to fifty percent (50%) to forty percent(40%) to thirty percent (30%) to twenty percent (20%) to ten percent(10%). Typically, the decreases in the duty cycle will be in smallerincrements.

The present invention allows the chef to set up recipes or themanufacturer to program recipes in which the intensity is independentlyset with different duty cycles and the spectrum of irradiation from thelamps independently set by selecting different power levels and thosedifferent settings can be changed periodically through the cooking cycleto achieve unique recipes for cooking special foods.

FIGS. 5-8 can be considered as either a graph of the power versus timefor all of the lamps or the power versus time for a single lamp, andsince the lamps can be controlled independently different lamps can beon at different times and following different power levels to controlthe spectrum and different duty cycles to control the intensity atdifferent times during the cooking process.

In a preferred embodiment of the present invention, applicable tocooking many different types of food such as thin and thick steaks,roasts, chickens, turkeys and other poultry, bread products, cakes,cookies and even frozen products, a fifty percent (50%) duty cycle isutilized during time period T₃, such as the lamps being on for threeseconds and off for three seconds, and then the duty cycle reduced to10:1 for the second lower reduced duty cycle during time T₅ such as withthe lamps on for one second and off for ten seconds.

The following examples show the timing for cooking various differenttypes of foods with maximum power indicated as one hundred percent(100%) intensity in each case:

    ______________________________________                                        Period    Time           Duty Cycle                                           ______________________________________                                        1. Carrot Cake - 100% Intensity                                               T.sub.1   11 sec.        on full                                              T.sub.2    3 sec.                                                             T.sub.3   16 sec.        3 sec. on/3 sec. off                                 T.sub.4    5 sec.                                                             T.sub.5   220 sec.       1 sec. on/10 sec. off                                T.sub.6    0 sec.                                                             2. Cinnamon Rolls - 100% Intensity                                            T.sub.1   20 sec.        on full                                              T.sub.2    0 sec.                                                             T.sub.3   30 sec.        3 sec. on/3 sec. off                                 T.sub.4    0 sec.                                                             T.sub.5   190 sec.       1 sec. on/6 sec. off                                 T.sub.6    0 sec.                                                             3. Turkey (9 pounds) - 100% Intensity                                         T.sub.1   165 sec.       on full                                              T.sub.2    0 sec.                                                             T.sub.3   160 sec.       3 sec. on/3 sec. off                                 T.sub.4    0 sec.                                                             T.sub.5   960 sec.       1 sec. on/3 sec. off                                 T.sub.6    0 sec.                                                             T.sub.7   480 sec.       1 sec. on/6 sec. off                                 T.sub.8    0 sec.                                                             ______________________________________                                    

While for maximum penetration into thick foods, full power is preferablyapplied to the lamps during the initial continuous power period T₁ andduring the reduced duty cycles, T₃ and T₅, there may be certain types offoods where the desired cooking of the food itself or specifically onesurface thereof is cooked using less than full power to certain or allof the lamps. Thus, the amount of radiation directed onto the food canbe reduced during a given period or a lower power level can be appliedto the lamps during a reduced duty cycle.

For example, FIG. 7 illustrates a continuously reduced power at a fiftypercent (50%) duty cycle from an initial time period T₁ of full power.

FIG. 8 illustrates a cooking recipe where both the power and the dutycycle are reduced following an initial cooking period T₁ of full powerat one hundred percent (100%) duty cycle.

The oven of the present invention may also be used cooperatively withother cooking sources. For example, the oven of the present inventionmay include a microwave radiation source. Such an oven would be idealfor cooking a thick highly absorbing food item such as a roast beef. Themicrowave radiation would be used to cook the interior portions of themeat and the infra-red and visible light radiation of the presentinvention would cook the outer portions. Further, the oven according tothe present invention could be used with a convection oven or with bothconvection oven and microwave oven cooking sources.

The present invention was described in relation to a preferredembodiment. However, it will be apparent to one skilled in the art thatone can change the parameters and still practice an invention within thespirit and scope of the present invention.

What is claimed is:
 1. The method of cooking food in a lightwave ovenhaving a plurality of high power lamps providing radiant energy in theelectromagnetic spectrum including a significant portion in thenear-visible and visible ranges comprising the steps of:irradiating thefood by applying power to at least one of said lamps without vaporizingall the surface water on the food for avoiding browning of the surfacethereby enabling deep penetration of the food by irradiation in thenear-visible and visible ranges, sensing a change in the water vaporconcentration emitted from the surface of the food to a predetermineddegree, terminating irradiation of the food and then applying reducedirradiation to the food.
 2. The method of cooking food in a lightwaveoven having a plurality of high power lamps providing radiant energy inthe electromagnetic spectrum including a significant portion in thenear-visible and visible ranges comprising the steps of:irradiating thefood by applying power to at least one of said lamps without vaporizingall the surface water on the food for avoiding browning of the surfacethereby enabling deep penetration of the food by irradiation in thenear-visible and visible ranges, sensing the amount of water vaporemitted from the surface of the food, terminating irradiation of thefood upon a predetermined decreased of water vapor in the oven and thenapplying reduced irradiation to the food.
 3. The method of cooking foodin a lightwave oven having a plurality of high power lamps providingradiant energy in the electromagnetic spectrum including a significantportion in the near-visible and visible ranges,irradiating the food byapplying power to at least one of said lamps without vaporizing all thesurface water on the food for avoiding browning of the surface therebyenabling deep penetration of the food by irradiation in the near-visibleand visible ranges, sensing the amount of water vapor emitted from thesurface of the food, terminating irradiation of the food upon an absenceof water vapor in the oven and then applying reduced irradiation to thefood.
 4. The method of cooking food in a lightwave oven having aplurality of high power lamps providing radiant energy in theelectromagnetic spectrum including a significant portion in the nearvisible and visible ranges comprising the steps of:irradiating the foodby applying power to at least one of said lamps without vaporizing allthe surface water on the food for avoiding browning of the surfacethereby enabling deep penetration of the food by irradiation in thenear-visible and visible ranges, sensing the amount of water vaporemitted from the surface of the food, terminating irradiation of thefood upon a predetermined decrease of water vapor in the oven and thenapplying reduced irradiation to the food.
 5. The method of cooking foodin a lightwave oven having a plurality of high power lamps providingradiant energy in the electromagnetic spectrum including a significantportion in the near-visible and visible ranges comprising the stepsof:irradiating the food by applying power to at least one of said lampswithout vaporizing all the surface water on the food for avoidingbrowning of the surface thereby enabling deep penetration of the food byirradiation in the near-visible and visible ranges, sensing the amountof water vapor emitted from the surface of the food, terminatingirradiation of the food upon an absence of water vapor in the oven andthen applying reduced irradiation to the food.
 6. The method of cookingfood in a lightwave oven having a plurality of high power lampsproviding radiant energy in the electromagnetic spectrum including asignificant portion in the near-visible and visible ranges comprisingthe steps of:irradiating the food by applying power to at least one ofsaid lamps without vaporizing all the surface water on the food foravoiding browning of the surface thereby enabling deep penetration ofthe food by irradiation in the near-visible and visible ranges and thenapplying reduced irradiation to the food, sensing a change in the watervapor concentration emitted from the surface of the food to thepredetermined degree and terminating irradiation of the food.
 7. Themethod of cooking food in a lightwave oven having a plurality of highpower lamps providing radiant energy in the electromagnetic spectrumincluding a significant portion in the near-visible and visible rangescomprising the steps of:irradiating the food by applying power to atleast one of said lamps without vaporizing all the surface water on thefood for avoiding browning of the surface thereby enabling deeppenetration of the food by irradiation in the near-visible and visibleranges, and then applying reduced irradiation to the food, sensing theamount of water vapor emitted from the surface of the food andterminating irradiation of the food upon a predetermined decrease ofwater vapor in the oven.
 8. The method of cooking food in a lightwaveoven having a plurality of high power lamps providing radiant energy inthe electromagnetic spectrum including a significant portion in thenear-visible and visible ranges comprising the steps of:irradiating thefood by applying power to at least one of said lamps without vaporizingall the surface water on the food for avoiding browning of the surfacethereby enabling deep penetration of the food by irradiation in thenear-visible and visible ranges, and then applying reduced irradiationto the food, sensing the amount of water vapor emitted from the surfaceof the food and terminating irradiation of the food upon an absence of awater vapor in the oven.
 9. The method of cooking food in a lightwaveoven having at least one high power lamp providing radiant energy in theelectromagnetic spectrum including a significant portion in thenear-visible and visible ranges comprising the steps of:irradiating thefood by applying power to said at least one lamp without vaporizing allof the surface water on the food for avoiding browning of the surfacethereby enabling deep penetration of the food by radiation in thenear-visible and visible ranges, sensing a change in the water vaporconcentration emitted from the surface of the food to a predetermineddegree and then turning off said at least one lamp until water isreplenished from within the food onto the surface of the food.
 10. Themethod of cooking food in a lightwave oven having at least one highpower lamp providing radiant energy in the electromagnetic spectrumincluding a significant portion in the near-visible and visible rangescomprising the steps of:irradiating the food by applying power to saidat least one lamp without vaporizing all of the surface water on thefood for avoiding browning of the surface thereby enabling deeppenetration of the food by radiation in the near-visible and visibleranges, sensing the amount of water vapor emitted from the surface ofthe food and then turning off said at least one lamp upon apredetermined decrease of water vapor in the oven until water isreplenished from within the food onto the surface of the food.
 11. Themethod of cooking food in a lightwave oven having at least one highpower lamp providing radiant energy in the electromagnetic spectrumincluding a significant portion in the near-visible and visible rangescomprising the steps of:irradiating the food by applying power to saidat least one lamp without vaporizing all of the surface water on thefood for avoiding browning of the surface thereby enabling deeppenetration of the food by radiation in the near-visible and visibleranges, sensing the amount of water vapor emitted from the surface ofthe food and then turning off said at least one lamp upon an absence ofwater vapor in the oven until water is replenished from within the foodonto the surface of the food.